Drive mechanism for rear-view mirror assembly of motor-driven folding type

ABSTRACT

A drive mechanism for an automatic rear-view mirror assembly of a motor-driven folding type. The driving mechanism includes an electric motor fixed on a mirror housing. The mirror housing is supported rotatably on a shaft fixed to a mirror base which is secured to a vehicle body in such a manner that it can be turned between a normal and retracted position by the drive mechanism. The drive mechanism includes a motor and a gear reducer composed of a plurality of planetary gear units. The planetary gear units include a sun gear connected to an output of the motor, and a group of transmission gears including a first spur gear mounted fixedly on the shaft and a second spur gear connected to an output shaft and meshed with the first spur gear. The reduction gear includes a first casing which houses the planetary gear units on the same shaft and has a ring gear common to these planetary gear units, provided on its inner circumferential surface. The reduction gear also includes a second casing which houses the remaining planetary gear units on the same shaft as the planetary gear units of the first unit, so that the planetary gear units of both casings are meshed with each other. The second casing also has a ring gear on its inner circumferential surface and a bolt by which the first and second casings are combined unitarily with each other. The ring gears of the first and second casings are formed with different gear modules, with the ring gear of the first casing being formed with a smaller gear module than that of the ring gear in the second casing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a drive mechanism for use in anautomotive side-view mirror assembly of a motor-driven folding type, andmore particularly to a drive mechanism destined for use in such a mirrorassembly to pivot in relation to the mirror base which is to be fixed toa car body the mirror housing supporting the mirror in such a mannerthat the latter can be turned vertically and horizontally, therebyfolding the mirror to the folded position or returning to the normalposition.

2. Prior Art

The drive mechanism for an automotive side-view mirror assembly of amotor-driven folding type comprises an electric motor fixed in a mirrorhousing, a speed reducer including reduction gears to reduce therevolution of the motor, and a device to convert the revolution outputof the speed reducer into a revolution of the mirror housing itself.Normally, remote-controlled mirror assemblies have disposed in themirror housing thereof a drive unit to turn the mirror itself verticallyand horizontally. Thus, the drive unit comprising a drive motor, speedreducer and converter is to be disposed in a limited space in the mirrorhousing.

The speed reducer forming a part of the drive unit used in suchautomotive side-view mirror of a motor-driven folding type is arelatively compact, lightweight one which uses planet gears in order toachieve a high reduction ratio. However, a single-stage speed reductionby a single planet gear cannot provide a desired reduction ratio.Normally, a multi-stage planet gear unit is used in the form of aplurality of planetary gear units housed in an elongated cylindricalcasing having common ring gears formed on the inner wall thereof. Moreparticularly, the required sizes of the ring gears, sun gears, planetgears and planet carriers in the multi-stage planetary gear unitdisposed in the limited space in the mirror housing are extremely small.Therefore, the manual assembling of the planetary gear units one by oneinto the elongated casing is very complicated and requires at thepresent great skill, much time and labor.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a drivemechanism for a rear-view mirror of a motor-driven folding type usingplanet gears which can be easily assembled without any great skill.

The above object is attained by providing a drive mechanism for aside-view mirror of a motor-driven folding type, comprising, accordingto the present invention, an electric motor capable of pivoting betweenthe normal position and the folded position, a mirror housing pivotablysupported on a shaft fixed to a mirror base which is to be fixed to acar body, a speed reducer comprising a plurality of planetary gear unitsincluding a sun gear coupled to an output shaft of the motor, and atransmission gear group including at least a spur gear fixed on theshaft and another spur gear coupled to the output shaft of the speedreducer and which is in mesh with the first spur gear, the speed reducercomprising a first cylindrical casing housing positioned coaxially withsome of the plurality of planetary gear units and which has formed onthe inner circumferential wall thereof a ring gear common to theabove-mentioned planetary gear units, a second cylindrical casinghousing positioned coaxially with the remaining planetary gear unitsamong the plurality of planetary gear units so as to be in mesh with theabove-mentioned planetary gear units and has formed on the innercircumferential face thereof a ring gear common to the remainingplanetary gear units, and a means for coupling together the first andsecond casings.

Since the casing assembly housing the plurality of planetary gear unitscomposing the speed reducer is of a longitudinally split structure,namely, it is composed of the first and second casings, some of theplanetary gear units can be housed in the first casing while theremaining planetary gear units be housed in the second casing. Thus, thedrive mechanism according to the present invention can be very easilyassembled without any great skill.

Also, because of the split structure of the casing assembly, a materialand module can be freely selected for each of the planetary gear unitshoused in the first and second casings, and thus the gear rigidity canbe designed more freely. More particularly, for planetary gear units atthe side of a motor of a low load torque, a material and module can beselected without the necessity of taking into consideration the largetorque of the planetary gear units at the output side. Therefore, sincethe module of the ring gear for the motor-side planetary gear units canbe kept to a small design, a higher reduction ratio can be provided andthe casing housing the motor-side planetary gear units can be made froma synthetic resin.

Furthermore, the first and second casings can be connected to each otherby a faucet joint. Thus, during assembling of the drive mechanism intothe mirror assembly, the first and second casings can be heldconcentrically with each other with the planetary gear units housedtherein, respectively, and the gears can be put into mesh with eachother with the casings being turned with respect to each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a motor-driven folding type rear-view mirrorassembly according to an embodiment of the present invention, showingthe internal structure with the mirror surface partially fragmented.

FIG. 2 is a partially sectional front view of the planet gear speedreducer forming a part of the drive mechanism shown in FIG. 1.

FIG. 3 is a schematic perspective exploded view (enlarged in scale) ofthe planet gear speed reducer.

FIG. 4 is a schematic, partially fragmental, exploded view of the planetgear speed reducer.

FIG. 5 is a schematic exploded view of the planet gear speed reducer,showing the faucet joint of the two casings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be hereinafter explained by way of example,with reference to the attached drawings.

FIGS. 1 thru 4 show an embodiment of the drive unit according to thepresent invention. In FIG. 1, the entire motor-driven folding typeside-view mirror is indicated with the reference numeral 10 and has amirror 12 covering the opening of a mirror housing 14 and which issupported pivotably in relation to the mirror housing 14. The mirrorhousing 14 has disposed therein a bracket 15 having fixed thereto amirror drive unit (not shown) comprising a drive motor to turn themirror 12 vertically and horizontally as remote-controlled. The mirrorhousing 14 is pivotably mounted on a shaft 20 fixed with a screw 18 to amirror base 16 which is to be fixed to a car body 17 (FIG. 1). Namely,the bracket 15 inside the mirror housing 14 has formed thereon coaxiallywith the shaft 20 a cylindrical portion 22 of which the inner diameteris slightly larger than the outer diameter of the shaft 20 and in whichthe shaft 20 is fitted. The shaft 20 has fitted thereon and disposed atthe base portion thereof a ring 24 which is also positioned in contactwith the lower opening edge of the cylindrical portion 22 to form athrust bearing. Also, the cylindrical portion 22 has formed in the lowerinner circumferential wall thereof a circular recess being somewhatlarger than the inner diameter of the cylindrical portion 22 and whichhouses an O-ring 26 which is in contact with the outer circumferentialsurface of the shaft 20 and the inner circumferential wall of thecylindrical portion 22. There is disposed a slide bearing 28 above theO-ring 26 and between the shaft 20 and cylindrical portion 22.

Such drive mechanism to turn about the shaft 20 and the mirror housing14 supported pivotably with respect to the shaft 20, comprises a motor30 fixed to the bracket 15 inside the mirror housing 14, reduction gears32 coupled to the output shaft of the motor 30, a first spur gear 34connected to the output shaft of the reduction gears 32, and a secondspur gear 36 in mesh with the first spur gear 34 and mounted on theshaft 20 as checked against any rotation, and which is axially movable.

When the mirror housing 14 is to be rotated as the motor 30 runs, therevolution of the motor 30 is transmitted to the first spur gear 34 bymeans of the reduction gears 32. The second spur gear 36, in mesh withthe first spur gear 34, is mounted on the shaft 20 as checked againstany rotation, namely, the second spur gear 36 has formed in the centerthereof an elongated hole of which the shape fits the circumference ofthe shaft 20 partially cut so as to have two opposite flat surfacesparallel to the axis of the shaft 20 above the top end of thecylindrical portion 22, so the first spur gear 34 moves around thesecond spur gear 36 as it rotates. There is provided a ring 38 betweenthe second spur gear 36 and the top end of the cylindrical portion 22.The shaft 20 has a spring seat 42 fixed near the top end thereof, andthere is interposed between the spring bearing 42 and the second spurgear 36 a compression coil spring 40 which forces the ring 38 to the topend of the cylindrical portion 22. The ring 38 forms a thrust bearingwhich lessens the friction between the top end of the cylindricalportion 22 and the mirror housing 14 when the latter rotates about theshaft 20. Thus, the ring 38 does not block the rotation of the mirrorhousing 14. The first spur gear 34 in mesh with the second spur gear 36,forms a clutch together with a holder 46. As will be described later, aportion of the output shaft 44 of the reduction gears 32 is shapedhexagonally. The holder 46 is fitted on the hexagonal portion androtates along with the output shaft 44. The holder 46 is axiallymovable. The first spur gear 34 is fitted on the output shaft 44 of thereduction gears 32 and forced to the holder 46 by a compression coilspring 35 interposed between the first spur gear 34 and the casing ofthe reduction gears 32. The end of the hexagonal portion of the outputshaft 44 on which the holder 46 is fitted is fixed to a seat member 48loose-fitted in a small hole formed in the bracket 15. There isinterposed between the bottom face of the holder 46 and the seat member48 a push nut 50 positioned for the first spur gear 34 to be in meshwith the second spur gear 36. Thus, when the mirror housing 14 is turnedas the motor 30 runs, the first spur gear 34 is forcibly pressed to theholder 46 by means of the compression coil spring 48, clutches theholder 46 and rotates along with the latter. When the mirror housing isturned by hand to the folded position, the first spur gear 34 isdisengaged from the holder 46 and becomes freely rotatable about theoutput shaft 44. The reference numeral 60 indicates a circular recessformed in the flat base portion of the shaft 20 around the axis of thelatter. The circular recess 60 is formed in a position corresponding tothe folded and used positions of the mirror housing 14. The bracket 15has formed therein a space housing a compression coil spring 64 and aball 66. The ball 66 is forced to the flat base portion of the shaft 20by means of the compression coil spring 64 and resiliently engaged inthe recess 60 when the mirror housing 14 is placed in the foldedposition or normal position.

As shown in FIGS. 2-4, the reduction gears 32 composing the drive unitfor a side-view mirror assembly of a motor-driven folding type iscomposed of four planetary gear units U1, U2, U3 and U4. FIG. 3 showsthe planetary gear units U1, U2 and U3 housed in a casing 70 havingformed in the inner cylindrical wall thereof a ring gear 72 common tothese three planetary gear units, while the planetary gear unit U4 ishoused in another casing 76 having another ring gear 74 formed in theinner wall thereof. The ring gears 72 and 74 are so formed as to have asame pitch circle diameter and they are jointed to each other withplural bolts 80 with the specified planetary gear units housed therein,respectively, to form the reduction gears or speed reducer 32. Further,the casing 70 has the motor 30 jointed thereto with a bolt 82, and thespeed reducer 32 and motor 30 are fixed together by the holder to thebracket 15 inside the mirror housing 46 (which is not shown).

As shown in FIG. 3, the planetary gear unit U1 comprises a sun gear 90fixed to the output shaft of the motor 30, three planet pinions 92 inmesh with the sun gear 90 as well as with the ring gear 72, and a planetcarrier 94 having three protrusions 96 loose-fitted in the respectiveplanet pinions 92 and thus supporting the planet pinions 92. Thisplanetary gear unit Ul decelerates one step and converts the revolutionof the motor 30 to a slower rotation of the planet carrier 94 (FIG. 4).

The planetary gear unit U2 similarly comprises a sun gear 190 fixed onthe shaft of the planet carrier 94 of the planetary gear unit U1, threeplanet pinions 192 in mesh with the sun gear 190 as well as with thering gear 72, and a planet carrier 194 having three protrusions 196loose-fitted in the respective planet pinions 192 and thus supportingthe planet pinions 192 (FIG. 4). This planetary gear unit U2 convertsthe rotation of the planet carrier 94 to a slower rotation of the planetcarrier 194.

Similar to the above planetary gear units, the planetary gear units U3and U4 comprise a sun gear 290 (390), three planet pinions 292 (392) inmesh with the sun gear 290 (390) as well as with the ring gear 72, and aplanet carrier 294 (394) having three protrusions 296 (396)loosely-fitted in the respective planet pinions 292 (392) and thussupporting the planet pinions 292. Planetary gear units U3 and U4convert the revolution of the motor 30 to a predetermined slow rotationof the last-stage planet carrier 394.

There is disposed as checked against any rotation on the shaft of theplanet carrier 394 composing the planetary gear unit U4, one end of theoutput shaft 44 which is to be coupled to the previously-mentionedclutch holder 46 (FIG. 1). The end of the output shaft 44 is shaped inthe form of a hexagon. The output shaft 44 is introduced through ahexagonal through-hole (not shown) formed in the clutch holder 46 andthe hexagonal end is secured to the seat member 48, the first spur gear34 is pressed by the compression coil spring 44 toward the clutch holder46 as loosely-fitted on the body of the output shaft 44.

Each of the ring gear 72, planet gears 90, 190 and 290, and planetpinions 92, 192 and 292 composing the U1 thru U3 planetary gear unitshas the module selected to be 0.4. The casing 70 having the ring gear 72formed on the inner circumferential wall thereof is made of nylon 66containing 30 percent glass by weight, the planet pinion 92 in mesh withthe sun gear 90 fixed to the output shaft of the motor 30 is made of asynthetic resin such as polyacetal or the like, and the remainder of thecomponent elements are made of a sintered alloy.

The module of each of the ring gear 74, sun gear 390 and planet pinion392 composing the planetary gear unit U4 is selected to be 0.5. Thecasing 76 having the ring gear 74 formed on the inner circumferentialwall thereof is made of a zinc die casting and the rest of the componentelements are made of a sintered alloy.

In this embodiment, the modules of the ring gears 72 and 74 are selectedto be 0.4 and 0.5, respectively. This is because the module of the ringgear 72 can be set small since the load torque of the ring gear 72 atthe side of the motor 30 is smaller than that of the ring gear 74 at theoutput side. Therefore, the number of teeth of the ring gear 72 can beincreased provided that the pitch circle diameters of the ring gears 72and 74 are equal to each other. In the conventional reduction gearsystem, a plurality of planetary gear units are disposed in a single diecasting-made casing having formed therein a ring gear common to theplanetary gear units. The module of the ring gear is determineddepending upon the load torque at the output side. Thus, it is notpossible to freely design the reduction ratio. However, the planetarygear mechanism forming the drive mechanism according to the presentinvention adopts such a structure of the casing in which a ring gear isformed and is split into two parts along a plane perpendicular to theaxis of the casing. The sub-casing at the motor side has disposedtherein three planetary gear units, while the sub-casing at the outputside has one planetary gear unit disposed therein. The modules of thetwo ring gears 72 and 74 can be determined depending upon the loadtorque at the motor side and that at the output side, respectively.Thus, a larger reduction ratio can be achieved. The planetary gear unitscan be assembled into the respective casings very easily and therigidity of the gears can be designed more freely.

FIG. 5 shows a variant of the planetary gear mechanism which providesfor easy and accurate positioning of the casings 70 and 76. The casings70 and 76 are jointed to each other by a faucet joint. Namely, the edgeof the end face of the casing 70 in which the ring gear 72 is formed isjointed to the casing 76, extended axially of the casing 70. Theextension rim 400 thus made and the joining end face of the casing 70define together a space receiving the end of the casing 76. The innerend of the casing 76 is so formed as to receive the extension rim 400 ofthe casing 70. When the casings 70 and 76 are coupled together, theouter circumferential receiving edge of the casing 76 fits the innercircumferential wall of the extension rim 400 of the casing 70. Afterthe planetary gear units Ul to U3 are housed in the casing 70 while theplanetary gear unit U4 is placed into the casing 76, the casings 70 and76 can be easily coupled with their axes aligned to each other owing tothe abovementioned faucet joint system. Namely, the faucet joint permitseasy and accurate positioning of the casings 70 and 76.

In the foregoing embodiments, the planetary gear units Ul, U2 and U3 arehoused in the casing 70 at the side of the motor 30, while the planetarygear unit U4 is housed in the casing 76 at the output side. However, thepresent invention is not limited to this configuration. Instead, theplanetary gear units Ul and U2 may be housed in the casing 70 while theplanetary gear units U3 and U4 be housed in the casing 76. Also, thecasings 70 and 76 having ring gears formed therein, respectively, aremade of different materials in the aforementioned embodiments, but theymay be made of a zinc die casting or a synthetic resin.

What is claimed is:
 1. A drive mechanism for a side-view mirror assemblyof the motor-driven folding type comprising:an electric motor to pivotbetween a normal and a folded position a mirror housing pivotablysupported on a shaft fixed to a mirror base which is to be fixed to acar body; a speed reducer comprising a plurality of planetary gear unitsincluding a sun gear coupled to an output shaft of said motor, and; atransmission gear group including at least a first spur gear fixed onsaid motor shaft and a second spur gear connected to an output shaft ofsaid speed reducer and which is in mesh with said first spur gear, saidspeed reducer comprising a first cylindrical casing, housing coaxiallysome of said plurality of planetary gear units including at least theplanetary gear unit including said sun gear coupled to the output shaftof said motor and which has formed on the inner circumferential wallthereof a first ring gear common to said some planetary gear units, asecond cylindrical casing, housing coaxially the remaining plurality ofplanetary gear units so as to be in mesh with said some planetary gearunits of the first cylindrical casing and has formed on the innercircumferential face thereof a second ring gear common to said remainingplanetary gear units, and a means for coupling together said first andsecond casings, said first and second ring gears being formed withdifferent gear modules such that the first ring gear formed in saidfirst casing is formed with a smaller gear module than that of thesecond ring gear formed in said second casing.
 2. A drive mechanism fora side-view mirror assembly of the motor-driven folding typecomprising:an electric motor to pivot between a normal and a foldedposition a mirror housing pivotably supported on a shaft fixed to a carbody; a speed reducer comprising a plurality of planetary gear unitsincluding a sun gear coupled to an output shaft said motor, and; saidspeed reducer comprising a first cylindrical casing, housing coaxiallysome of said plurality of planetary gear units and which has formed onthe inner circumferential wall thereof a first ring gear common to saidsome planetary gear units, a second cylindrical casing, housingcoaxially the remaining planetary gear units so as to be in mesh withsaid some planetary gear units and has formed on the innercircumferential face thereof a second ring gear common to said remainingplanetary gear units, and a means for coupling together said first andsecond casings; said first and second ring gears being formed withdifferent gear modules wherein the gear module of said first ring gearis dependent upon a load torque at said motor output shaft, and the gearmodule of said second ring gear is dependent upon a greater load torqueat said output shaft of the speed reducer.
 3. A drive mechanismaccording to claim 2, wherein said first casing houses at least theplanetary gear unit including said sun gear coupled to the output shaftof said motor and the first ring gear formed in said first casing isformed with a smaller gear module than that of the second ring gearformed in said second casing.
 4. A drive mechanism according to claim 3,wherein said first casing is made of a synthetic resin while said secondcasing is made of die casting.
 5. A drive mechanism according to claim2, wherein the opening ends of said first and second casings have faucetjoints formed thereon, respectively.
 6. A drive mechanism for aside-view mirror assembly of a motor-driven folding type comprising:anelectric motor to pivot between a normal and a folded position a mirrorhousing pivotably supported on a shaft fixed to a mirror base which isto be fixed to a car body; a speed reducer comprising a plurality ofplanetary gear units including a sun gear coupled to an output shaft ofsaid motor, and; said speed reducer comprising a first cylindricalcasing, housing coaxially some of said plurality of planetary gear unitsand which has formed on the inner circumferential wall thereof a firstring gear common to said some planetary gear units, a second cylindricalcasing housing coaxially the remaining plurality of planetary gear unitsso as to be in mesh with said some planetary gear units and has formedon the inner circumferential face thereof a second ring gear common tosaid remaining planetary gear units, and a means for coupling togethersaid first and second casings, and wherein said first casing is made ofa synthetic resin and said second casing is made of a die casting.
 7. Adrive mechanism according to claim 6, wherein said first and second ringgears are formed with different gear modules.
 8. A drive mechanismaccording to claim 7, wherein said first casing houses at least theplanetary gear unit including said sun gear coupled to the output shaftof said motor and the first ring gear is formed with a smaller gearmodule than that of the second ring gear.
 9. A driven mechanism for aside-view mirror of a motor-driven folding type comprising:an electricmotor to pivot between a normal and a folded position a mirror housingpivotably supported on a shaft fixed to a mirror base which is to befixed to a car body; a speed reducer comprising a plurality of planetarygear units including a sun gear coupled to an output shaft of saidmotor, and; a transmission gear group including at least a spur gearfixed on said motor shaft and another spur gear coupled to an outputshaft of said speed reducer and which is in mesh with said first spurgear, said speed reducer comprising a first cylindrical casing, housingcoaxially some of said plurality of planetary gear units and which hasformed on the inner circumferential wall thereof a first ring gearcommon to said some planetary gear units, a second cylindrical casing,housing coaxially the remaining plurality of planetary gear units so asto be in mesh with said some planetary gear units in the first casingand has formed on the inner circumferential face thereof a second ringgear common to said remaining planetary gear units and a means forcoupling together said first and second casings, said first and secondring gears being formed with different gear modules, and wherein saidsome plurality of planetary gear units are arranged in said first casingso as to provide a higher gear reduction ratio and said remainingplurality of said planetary gear units are arranged in said secondcasing so as to be adapted to the greater torque at said output shaft ofthe speed reducer.
 10. A drive mechanism according to claim 9, whereinsaid first casing houses at least the planetary gear unit including saidsun gear coupled to the output shaft of said motor and the first ringgear formed in said first casing is formed with a smaller gear modulethan that of the second ring gear formed in said second casing.
 11. Adrive mechanism according to claim 9, wherein said first casing is madeof a synthetic resin while said second casing is made of a die casting.12. A drive mechanism according to claim 9, wherein the opening ends ofsaid first and second casings have faucet joints formed thereon,respectively.